A little while back, some of you were kind enough to help a non-mechanical F150 owner...well, I'm back with another mystery problem.

I was driving home this evening in my 2000 F150 (small V8) and the engine stopped. Steering became sluggish and I drifted to the curb. Found that the F18 shorted out. After I replaced it, I could not get the engine to turn over so I replaced the battery (almost at 120k miles on the original). Then it turned over fine and I started driving, and it died again. The F18 blew out once more. In the end, I shorted 4 15A fuses this evening and 2 20A because that is what I had with me and they all kept shorting out. Finally made it to the drive way (coasted in). When the ignition is turned to the on position, the "theft" light and the overdrive light on the end of the shift handle are blinking rapidly and I can hear a rapid clicking sound.

Any ideas or help for the mechanically declined?

Thanks!

 

Do you have any mods done to the truck? Any work done reciently?

JMC

 

No sir. Not other than an oil change...though I did disconnect the cruise control connection in front of the brake fluid reservoir back in May.

 

There is a short to ground in that circuit. It powers the MAF, all 8 injectors, the IAC valve, and the Fuel pump relay. I would unplug the fuse and check for continuity to ground. Check the wires going to the MAF, the injectors for signs of chafing. It is the red wire.

JMC

 

JMC,

Thanks for the insight. I used an ohm meter to check and got consistent readings at 5.5 on the meter for each injector and the MAF (unplugged it along the air intake). What do you mean by chafing? Concerning the MAF, is there more to do than unplugging it and checking the ohm meter at the fuse inlet?

Thanks!!!

 

By chafing I mean to rub on something to the point that the insulation is exposed. Happened to the wires going to my MAF. The red one touched metal and blew the same fuse you are having trouble with. There should be no continuity to ground with the key off and the fuse removed.

JMC

 

JMC,

Please pardon my ignorance about this, since the ohm meter was reading pretty consistent, would that indicate it is not chafing? Or is a visual inspection the way to go?

Thanks!

 

I would inspect the wires for visual signs first. Then pull the fuse and set the meter to continuity setting. Probe the circuit for continuity to ground. Set meter to ohms. Groind the black probe to the chasie and probe the circuit with the red probe. It should indicate 0 or very close to that if there is continuity. Some digital meters have a setting which will indicate contunity with a beep.

JMC

 

JMC,

I did not see signs of chafing in addition to testing the circuit (MAF and injectors were all unplugged & tested). Any idea of what I should do next?

Thanks!

 

Ground one of the meter probes and touch the red wire in the MAF connector with the other one. The OHMS should not read 0.

JMC

 

Ok, I checked the wire in the MAF connector with the red stripe (there was not a solid red one). The Ohm meter went to zero. Does that mean the wiring is grounded and I would need to replace the wire?

Thanks!

 

There should be 4 wires going to the MAF sensor. Red, Black with White stripe, Tan with Light Blue stripe and Light Blue with Red stripe. If you are missing the Red wire it could be hanging and casuing the short.

JMC

 

I went and got a Haynes Repair manual and I can see a red wire, separate from the other three, in the diagram going to the MAF. Do you know where it should connect to the MAF at?

Thanks!

 

Have a look at this pic of the connector. It shows 4 wires.

JMC

 

Maybe I am blind...the plug I am looking at only has three wires and three contact points in it. I pulled it from the attachment on the right (as you face it from the front) of the metal casing where the air intake duct meets the engine next to the IAC. The diagram in my book show 4 wires, too, but the red is shown separately from the other three. It shows the red wire coming in from the PCM. Any ideas?

JMC - Thanks very much for your patience working through this!